Insight into suppression of dibutyl phthalate on DOM removal during municipal sewage treatment using fluorescence spectroscopy with PARAFAC and moving-window 2D-COS

Abstract

Dibutyl phthalate (DBP) has been widely detected in municipal and industrial wastewater, which could indirectly inhibit pollutant removals, especially degradation of dissolved organic matter (DOM). Here, the inhibition of DBP on DOM removal from wastewater in pilot-scale A2O-MBR system was investigated by fluorescence spectroscopy with two-dimensional correlation (2D-COS) and structural equation modeling (SEM). Seven components were extracted from DOM using parallel factor analysis, i.e., tryptophan-like (C1 and C2), fulvic-like (C4), tyrosine-like (C5), microbial humic-like (C6) and heme-like (C7). The tryptophan-like had a blue-shift at DBP occurrence, defined as blue-shift tryptophan-like (C3). DBP with 8 mg L−1 exhibited a stronger inhibition on removals of DOM fractions, extraordinarily tyrosine-like and tryptophan-like in anoxic unit than DBP of 6 mg L−1 by moving-window 2D-COS. The indirect removals of C1 and C2 through the C3 removal were more strongly inhibited by 8 mg L−1 DBP than those by 6 mg L−1 DBP, while the former exhibited a weaker inhibition on the direct degradation of C1 and C2 than the latter via SEM. Based on metabolic pathways, abundances of key enzymes secreted by microorganism in anoxic unit, degrading tyrosine-like and tryptophan-like, were higher in wastewater with 6 mg L−1 DBP than those with 8 mg L−1 DBP. These could provide a potential approach for online monitoring of DBP concentrations in wastewater treatment plants, which could rectify operating parameters, and then enhance the treatment efficiencies.